[FFmpeg-cvslog] avcodec/jpeg2000dec: Move preparations to main thread, fix race
Andreas Rheinhardt
git at videolan.org
Sat Jan 29 21:02:07 EET 2022
ffmpeg | branch: master | Andreas Rheinhardt <andreas.rheinhardt at outlook.com> | Thu Jan 27 15:53:48 2022 +0100| [218d1f76d46fc5b59a27d5ec9e88e821dc888d11] | committer: Andreas Rheinhardt
avcodec/jpeg2000dec: Move preparations to main thread, fix race
jpeg2000_decode_tile() (which is run concurrently by several threads
when using slice threading) currently modifies some joint values
before doing its actual work. This is a data race that happens to work
because all threads set the same values; but it is nevertheless
undefined behaviour.
Fix this by performing said preparatory work in the main thread instead.
This fixes the vsynth(1|2|_lena)-jpeg2000(-97)? FATE-tests when using
TSAN and slice threading.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=218d1f76d46fc5b59a27d5ec9e88e821dc888d11
---
libavcodec/jpeg2000dec.c | 23 +++++++++++------------
1 file changed, 11 insertions(+), 12 deletions(-)
diff --git a/libavcodec/jpeg2000dec.c b/libavcodec/jpeg2000dec.c
index 80b2e2d627..a7eb809f30 100644
--- a/libavcodec/jpeg2000dec.c
+++ b/libavcodec/jpeg2000dec.c
@@ -2080,7 +2080,6 @@ static int jpeg2000_decode_tile(AVCodecContext *avctx, void *td,
Jpeg2000DecoderContext *s = avctx->priv_data;
AVFrame *picture = td;
Jpeg2000Tile *tile = s->tile + jobnr;
- int x;
tile_codeblocks(s, tile);
@@ -2088,17 +2087,6 @@ static int jpeg2000_decode_tile(AVCodecContext *avctx, void *td,
if (tile->codsty[0].mct)
mct_decode(s, tile);
- for (x = 0; x < s->ncomponents; x++) {
- if (s->cdef[x] < 0) {
- for (x = 0; x < s->ncomponents; x++) {
- s->cdef[x] = x + 1;
- }
- if ((s->ncomponents & 1) == 0)
- s->cdef[s->ncomponents-1] = 0;
- break;
- }
- }
-
if (s->precision <= 8) {
write_frame_8(s, tile, picture, 8);
} else {
@@ -2537,6 +2525,17 @@ static int jpeg2000_decode_frame(AVCodecContext *avctx, void *data,
if (ret = jpeg2000_read_bitstream_packets(s))
goto end;
+ for (int x = 0; x < s->ncomponents; x++) {
+ if (s->cdef[x] < 0) {
+ for (x = 0; x < s->ncomponents; x++) {
+ s->cdef[x] = x + 1;
+ }
+ if ((s->ncomponents & 1) == 0)
+ s->cdef[s->ncomponents-1] = 0;
+ break;
+ }
+ }
+
avctx->execute2(avctx, jpeg2000_decode_tile, picture, NULL, s->numXtiles * s->numYtiles);
jpeg2000_dec_cleanup(s);
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